Grundy County, Iowa
A shallow water table limits basements on 67% of Grundy County's mapped land, a higher share than 79% of US counties. Shrink-swell clay limits houses without basements on 59%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list no flood losses here since 2016. 75% of homes were built before 1980, against 50% nationally; the median home dates from 1962.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Grundy County
| Expansive clay (limits slab homes) | 58.9% |
| High water table (limits basements) | 66.9% |
| Septic fields very limited | 99.4% |
| Clay swell (LEP, by area) | 4.6% |
| High-swell land (LEP 6%+) | 3.3% |
| Mapped soil | 320,800 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Tama | 28% | 0% |
| Colo | 12% | n/a |
| Muscatine | 11% | n/a |
| Dinsdale | 8% | n/a |
| Kenyon | 7% | n/a |
| Ely | 5% | n/a |
How we count · survey areas IA075 (2025-09-08)
What the numbers mean here
Clay swell averages a linear extensibility of 4.6% by land area here, and 3% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 59% of the mapped land.
On 67% of Grundy County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
Rain over the 12 months to August 2026: 37.06 in, 0.69 in above the 1991-2020 average year of 36.37 in.
USDA rates 99% of the land very limited for septic absorption fields.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. No part of the county was in drought in the last 52 weeks.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 0% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Grundy County since 2016.
Rain
| Average year, 1991-2020 | 36.37 in |
| 12 months to August 2026 | 37.06 in (+0.69) |
| 2025 | 37.06 in (+0.69) |
| Wettest year since 1895 | 1993: 50.99 in |
| Driest year since 1895 | 1988: 19.69 in |
| Days with 1 inch or more, normal at GRUNDY CTR (3 mi away) | 9.1 |
Homes
| Housing units | 5,498 |
| Median year built | 1962 |
| Built before 1980 | 75% |
| Built 2000 or later | 13% |
| Owner-occupied | 85% |
| Median value, owner-occupied | $198,800 |
| Single-family detached | 85% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Butler County, IA | 23 mi | 9% | 73% |
| Hardin County, IA | 23 mi | 17% | 57% |
| Black Hawk County, IA | 26 mi | 9% | 75% |
| Tama County, IA | 26 mi | 42% | 49% |
| Marshall County, IA | 27 mi | 42% | 47% |
| Franklin County, IA | 34 mi | 13% | 72% |
| Bremer County, IA | 35 mi | 4% | 78% |
| Story County, IA | 43 mi | 9% | 64% |
Sources: USDA SSURGO (September 8, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status